Epstein-Barr virus (EBV) is a gamma herpesvirus that causes infectious mononucleosis and is associated with a variety of human lymphoid and epithelial cancers. Immunocompromise is a risk factor for EBV associated disease with malignancies such as post-transplant lymphoproliferative disease arising in transplant patients and central nervous system lymphoma and a proportion of systemic lymphomas being EBV associated in AIDS patients. EBV is also associated with Burkitt' s lymphoma, nasopharyngeal carcinoma, nasal T cell lymphoma, and a subset of Hodgkin' s lymphomas and gastric carcinomas. After primary infection an individual will remain latently infected with EBV and it is this life-long reservoir of latently infected cells that is a factor in the development of subsequent malignant disease. [unreadable] [unreadable] EBV infection of B cells in culture leads to the outgrowth of immortalized B cell lines and EBNA2 is one of the EBV encoded proteins essential for this process. EBNA2 alters cellular gene expression by targeting a DNA binding protein, CBF1/RBPJk, and switching CBF1 repressed promoters to an activated state. In its targeting of CBF1, EBNA2 mimics activated Notch signaling. A recently recognized ORF present in the EBV BARTs encodes a protein, RPMS, that also interacts with the Notch pathway, in this case negatively regulating Notch activity. The goal of this research program is to understand the contribution of EBNA2 to EBV driven B cell immortalization and the role of RPMS in latency maintainance and in EBV associated epithelial malignancies. The Specific Aims are: [1] To examine EBNA2 mediated cell survival activities by generating an EBV mutant defective for Nur77 binding and further characterizing the EBNA2-Nur77 interaction and its consequences. [2] To identify and compare the downstream targets of EBNA2 and NotchIC. Primary B cells and EBV negative B cell lines will be infected with lentivirus vectors expressing EBNA2 or NotchIC and with EBV EBNA2 mutant viruses and the changes induced in cell gene expression will determined using gene array technologies. [3] To examine RPMS function and the regulation of RPMS stability. The contribution of phosphorylation to RPMS protein turnover and proteosomal targeting will be examined and the potential role of RPMS anti-Notch activity in epithelial tumor development will be probed.